Commit fe4f3eb1 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
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perf probe: Add permission and sysctl notice to man page 



Add a section to notify the permission and sysctl setting for perf
probe. And fix some indentations.

Reported-by: default avatarRavi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: default avatarRavi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/162204068898.388434.16842705842611255787.stgit@devnote2


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 67e446eb

tools/perf/Documentation/perf-probe.txt

+16 −3
Original line number Diff line number Diff line
@@ -295,6 +295,19 @@ Add a probe in a source file using special characters by backslash escape 
 ./perf probe -x /opt/test/a.out 'foo\+bar.c:4'





PERMISSIONS AND SYSCTL

----------------------

Since perf probe depends on ftrace (tracefs) and kallsyms (/proc/kallsyms), you have to care about the permission and some sysctl knobs.



 - Since tracefs and kallsyms requires root or privileged user to access it, the following perf probe commands also require it; --add, --del, --list (except for --cache option)



 - The system admin can remount the tracefs with 755 (`sudo mount -o remount,mode=755 /sys/kernel/tracing/`) to allow unprivileged user to run the perf probe --list command.



 - /proc/sys/kernel/kptr_restrict = 2 (restrict all users) also prevents perf probe to retrieve the important information from kallsyms. You also need to set to 1 (restrict non CAP_SYSLOG users) for the above commands. Since the user-space probe doesn't need to access kallsyms, this is only for probing the kernel function (kprobes).



 - Since the perf probe commands read the vmlinux (for kernel) and/or the debuginfo file (including user-space application), you need to ensure that you can read those files.





SEE ALSO

--------

linkperf:perf-trace[1], linkperf:perf-record[1], linkperf:perf-buildid-cache[1]